Antioxidant Activity and Biological Studies of Two Medicinal Plant Extracts on Spodoptera littoralis (Boisd)

Control management of Spodoptera littoralis (Boisd) infestation has been achieved by using chemical insecticides. However, the environment-friendly methods without unwanted side effects of these chemicals are becoming very important in modern pest management strategies. Natural products including plant ethanolic extracts and essential oils are some of the alternative approaches in pest control. The essential oils were extracted and their chemical composition was identified using a GC/MS spectrometer. Therefore, the present study was designed to evaluate the antioxidant activity of various extracts of sage and thyme plants by 2, 2-diphenyl-1-picrylhydrazil (DPPH) method. The obtained results revealed that concentrations at 25, 50, 100 and 200µg/ml of essential oils and ethanolic extract from both plants were more efficient in scavenging free radicals after 30 min when compared with butyl hydroxyl toluene(BHT) as synthetic standard. The concentrations 100 and 200µg/mL from ethanolic and essential oils were having higher activity than other extracts and standard .Furthermore, Sage and thyme extracts were investigated for their toxicity against cotton leafworm, S. littoralis in the laboratory, the percentages of cumulative mortality of larvae as well as the latent effects of the 4th instar of S. littoralis four concentrations (25, 50, 100 and 200 µg/mL) were applied. It was found that ethanolic extract of two plants was more efficient than essential oils on different stages of S. littoralis. The results showed that there were highly significant differences between all treatments and control some biological aspects.